Since 2011, with the approval of crizotinib and subsequent approval of four additional targeted therapies, anaplastic lymphoma kinase (ALK) inhibitors have become important treatments for a subset of patients with lung cancer. Each generation of ALK inhibitor showed improvements in terms of central nervous system (CNS) penetration and potency against wild-type (WT) ALK, yet a key continued limitation is their susceptibility to resistance from ALK active-site mutations. The solvent front mutation (G1202R) and gatekeeper mutation (L1196M) are major resistance mechanisms to the first two generations of inhibitors while patients treated with the third-generation ALK inhibitor lorlatinib often experience progressive disease with multiple mutations on the same allele (mutations in cis, compound mutations). TPX-0131 is a compact macrocyclic molecule designed to fit within the ATP-binding boundary to inhibit ALK fusion proteins. In cellular assays, TPX-0131 was more potent than all five approved ALK inhibitors against WT ALK and many types of ALK resistance mutations, e.g., G1202R, L1196M, and compound mutations. In biochemical assays, TPX-0131 potently inhibited (IC50 <10 nmol/L) WT ALK and 26 ALK mutants (single and compound mutations). TPX-0131, but not lorlatinib, caused complete tumor regression in ALK (G1202R) and ALK compound mutation-dependent xenograft models. Following repeat oral administration of TPX-0131 to rats, brain levels of TPX-0131 were approximately 66% of those observed in plasma. Taken together, preclinical studies show that TPX-0131 is a CNS-penetrant, next-generation ALK inhibitor that has potency against WT ALK and a spectrum of acquired resistance mutations, especially the G1202R solvent front mutation and compound mutations, for which there are currently no effective therapies.

Abstract Three generations of ALK inhibitors are approved for the treatment of ALK+ NSCLC but their efficacy is often limited by ALK resistance mutations. The solvent front mutation G1202R and gatekeeper mutation L1196M are major resistance mechanisms to the first two generations of inhibitors. Patients treated with second generation inhibitors are reported to progress with multiple mutations on separate alleles (mutations in trans). In contrast, 35 - 48% of patients treated with lorlatinib progress with multiple mutations on the same allele (compound mutations, mutations in cis). TPX-0131 is an ALK inhibitor with a compact macrocyclic structure designed to bind completely within the ATP binding boundary and overcome a spectrum of single and compound ALK resistant mutations. TPX-0131 was profiled against previous generations of ALK inhibitors both in vitro and in vivo. In biochemical assays, TPX-0131 potently inhibits (IC50 <10 nM) wild type (WT) ALK and 26 ALK mutations (single and compound). Cell proliferation assays of WT, single mutations, and compound mutations were used to evaluate TPX-0131 relative to previous generations of ALK inhibitions (crizotinib, alectinib, brigatinib, ceritinib, lorlatinib). TPX-0131 is more potent against WT EML4-ALK (IC50 = 0.4 nM) than previous generations of ALK inhibitors (2-fold, lorlatinib; 10 - 30-fold, second generation inhibitors; >100-fold, crizotinib). TPX-0131 potently inhibits EML4-ALK harboring a G1202R solvent front mutation (IC50 = 0.2 nM) which is >100-fold more potent than previous generations of ALK inhibitors. TPX-0131 potently inhibits ALK harboring a gatekeeper mutation (IC50 = 0.5 nM) and is >10-fold more potent than previous generations of ALK inhibitors. TPX-0131 potently inhibits ALK with a L1198F hinge area mutation (IC50 = 0.2 nM) which is 87 - 3000-fold more potent than previous generations of ALK inhibitors. TPX-0131 is the most potent inhibitor against nine EML4-ALK double and triple compound mutations (6 with IC50 < 1 nM, 3 with IC50 1.6 - 14.9 nM). Evaluation of ALK phosphorylation as a pharmacodynamic marker in tumors showed potent ALK inhibition by TPX-0131 that correlated with TPX-0131 exposure. In Ba/F3 cell-derived xenograft tumor models with EML4-ALK mutations, TPX-0131 (2, 5, 10 mg/kg BID) demonstrated robust anti-tumor activity in the G1202R model (64%, 120%, 200% TGI), G1202R/L1198F model (complete regression, all doses), and G1202R/L1196M model (44%, 83% and 200% TGI). In contrast, lorlatinib (5 mg/kg BID) caused 31% TGI in the G1202R/L1198F model and did not have statistically significant TGI in the G1202R/L1196M model. Taken together, TPX-0131 is a next generation ALK inhibitor that has preclinical potency against WT ALK as well as a broad spectrum of acquired resistance mutations, especially compound mutations, which currently lack any effective ALK inhibitor therapy. Citation Format: Brion W. Murray, Dayong Zhai, Wei Deng, Evan Rogers, Xin Zhang, Jane Ung, Vivian Nguyen, Han Zhang, Maria Barrera, Ana Parra, Jessica Cowell, Dong Lee, Herve Aloysius. TPX-0131, a potent inhibitor of wild type ALK and a broad spectrum of both single and compound ALK resistance mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1469.

Abstract Anaplastic lymphoma kinase (ALK) gene rearrangements occur in up to 7% of patients with non-small cell lung cancer (NSCLC) with the majority as EML4-ALK fusions. Crizotinib (first generation ALK inhibitor) was the first approved ALK inhibitor for the treatment of ALK-positive metastatic non-small cell lung cancer. However, development of resistance to crizotinib caused by secondary kinase domain mutations, bypass signaling, or morphology changes occurs. Second generation ALK inhibitors alectinib, ceritinib, and brigatinib were able to overcome the majority of ALK resistant mutations (L1196M, G1269A and F1174L) acquired with crizotinib. The solvent front mutation (SFM) G1202R is a common resistant mutation to crizotinib and the second generation ALK inhibitors. Lorlatinib, a third generation ALK inhibitor, can overcome G1202R resistance with moderate IC50 values of 40 - 60 nM in cell-based assays. Although, compound mutations such as ones with both gatekeeper and solvent front mutations (L1196M/G1202R) are refractory to lorlatinib, representing an unmet medical need. TPX-0131 is a next generation ALK inhibitor designed with a compact macrocyclic structure that can bind completely within the ATP binding boundary to overcome a variety of ALK resistant mutations, especially SFM G1202R and compound mutations L1196M/G1202R. TPX-0131 potently inhibits wildtype (WT) ALK and over 20 different ALK mutations with IC50 values <5 nM when tested in enzymatic kinase assays in the presence of 10 μM of ATP. In cell proliferation assays, TPX-0131 exhibited comparable antiproliferation activity to the most potent ALK inhibitor lorlatinib in Ba/F3 cells engineered with EML4-ALK WT. Importantly, TPX-0131 is more than 100-fold more potent against G1202R than lorlatinib in cell proliferation assays. Furthermore, TPX-0131 demonstrated antiproliferation IC50 values <2 nM in Ba/F3 cell models engineered with compound mutations including L1196M/G1202R, L1198F/G1202R, L1196M/L1198F, and C1156Y/G1202R, while lorlatinib and other ALK inhibitors are not active (IC50s >1 μM). Taken together, TPX-0131 is a next generation ALK inhibitor that can overcome a broad spectrum of acquired resistance mutations, especially the G1202R solvent front mutation and compound mutations (e.g. L1196M/G1202R). The nonclinical pharmacology profile of TPX-0131 warrants further preclinical investigation. Citation Format: J. Jean Cui, Evan Rogers, Dayong Zhai, Wei Deng, Jane Ung, Vivian Nguyen, Han Zhang, Xin Zhang, Ana Parra, Maria Barrera, Dong Lee, Brion Murray. TPX-0131: A next generation macrocyclic ALK inhibitor that overcomes ALK resistant mutations refractory to current approved ALK inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5226.

Anaplastic lymphoma kinase (ALK) gene rearrangements occur in up to 7% of patients with non-small cell lung cancer (NSCLC) with the majority as EML4-ALK fusions. Crizotinib (first generation ALK inhibitor) was the first approved ALK inhibitor for the treatment of ALK-positive metastatic non-small cell lung cancer. However, development of resistance to crizotinib caused by secondary kinase domain mutations, bypass signaling, or morphology changes occurs. Second generation ALK inhibitors alectinib, ceritinib, and brigatinib were able to overcome the majority of ALK resistant mutations (L1196M, G1269A and F1174L) acquired with crizotinib. The solvent front mutation (SFM) G1202R is a common resistant mutation to crizotinib and the second generation ALK inhibitors. Lorlatinib, a third generation ALK inhibitor, can overcome G1202R resistance with moderate IC50 values of 40 - 60 nM in cell-based assays. Although, compound mutations such as ones with both gatekeeper and solvent front mutations (L1196M/G1202R) are refractory to lorlatinib, representing an unmet medical need. TPX-0131 is a next generation ALK inhibitor designed with a compact macrocyclic structure that can bind completely within the ATP binding boundary to overcome a variety of ALK resistant mutations, especially SFM G1202R and compound mutations L1196M/G1202R. TPX-0131 potently inhibits wildtype (WT) ALK and over 20 different ALK mutations with IC50 values 1 μM). Taken together, TPX-0131 is a next generation ALK inhibitor that can overcome a broad spectrum of acquired resistance mutations, especially the G1202R solvent front mutation and compound mutations (e.g. L1196M/G1202R). The nonclinical pharmacology profile of TPX-0131 warrants further preclinical investigation. Citation Format: J. Jean Cui, Evan Rogers, Dayong Zhai, Wei Deng, Jane Ung, Vivian Nguyen, Han Zhang, Xin Zhang, Ana Parra, Maria Barrera, Dong Lee, Brion Murray. TPX-0131: A next generation macrocyclic ALK inhibitor that overcomes ALK resistant mutations refractory to current approved ALK inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5226.

3616 Background: RET fusions/mutations drive oncogenesis in lung and thyroid cancers, and several other malignancies. Selective RET inhibitors (selpercatinib/pralsetinib) are active in patients with these cancers; unfortunately, resistance often occurs. On-target resistance includes the acquisition of solvent front mutations (SFMs i.e. RET G810 substitutions). TPX-0046 is a structurally differentiated RET inhibitor that is potent against a range of RET fusions and mutations including SFMs. Methods: The rationally-designed, compact, macrocyclic RET/SRC inhibitor TPX-0046 was characterized in RET-driven in vitro and in vivo tumor models. Results: In enzymatic assays, TPX-0046 showed low nanomolar potency against wild-type RET and 18 RET mutations/fusions. It was potent against SRC and spared VEGFR2/KDR. TPX-0046 inhibited RET phosphorylation (IC50 < 10 nM) in tumor cell lines (LC2/ad, CCDC6-RET; TT, RET C634W) and Ba/F3 engineered RET models (WT, G810R). In cell proliferation assays, TPX-0046 inhibited KIF5B-RET Ba/F3, LC2/ad, and TT cells with IC50 values ~1 nM. Ba/F3 RET engineered cells with SFMs (e.g. G810C/R/S) were potently inhibited by TPX-0046 (mean proliferation IC50 1–17 nM). TPX-0046 demonstrated marked in vivo anti-tumor efficacy in RET-driven cell-derived and patient-derived xenograft tumor models. In a Ba/F3 KIF5B-RET xenograft model, a single dose of 5 mg/kg TPX-0046 inhibited > 80% of RET phosphorylation (corresponding mean free plasma concentration: 51 nM). At 5 mg/kg BID, tumor regression was observed in RET-dependent xenograft models, including those that harbor RET SFMs: TT, CTG-0838 PDX (NSCLC, KIF5B-RET), CR1520 PDX (CRC, NCOA4-RET), Ba/F3 KIF5B-RET, and Ba/F3 KIF5B-RET G810R. Conclusions: TPX-0046 is a unique next-generation RET inhibitor that possesses potent in vitro and in vivo activity against a diverse range of RET alterations, including SFM-mediated resistance. A phase 1/2 trial for RET inhibitor-resistant and naïve RET-driven cancers is on-going (NCT04161391).

Aberrant activation of the HGF/MET pathway has frequently been found in human cancers via MET mutation, gene amplification and translocation, as well as HGF paracrine or autocrine upregulation. The abnormal HGF/MET signaling not only acts as an oncogenic driver but also confers resistance to many cancer therapies, such as EGFR targeted therapy in NSCLC. One key downstream effector for activated MET is SRC, which is also involved in malignancy formation, tumor metastasis and drug resistance. In the tumor microenvironment, CSF1R plays an important role in regulation of tumor associated macrophages, which promote tumor progression and angiogenesis. Therefore, the polypharmacological inhibition of MET/SRC/CSF1R has great potential for more effectively targeting cancers with abnormal HGF/MET signaling via targeting both tumor intrinsic signaling and the tumor microenvironment. TPX-0022, a novel macrocyclic compound, has been designed and optimized to inhibit MET/CSF1R/SRC with enzymatic kinase inhibition IC50s of 0.14, 0.76 and 0.12 nM, respectively. TPX-0022 potently inhibited cell proliferation of the MET-amplified MKN-45 and SNU-5 gastric cancer cells, with IC50s <0.2 nM, which ranked TPX-0022 as one of the most potent MET inhibitors. TPX-0022 caused suppression of MET auto-phosphorylation at an IC50 of approximately 0.3 nM in MKN-45 cell line. TPX-0022 also potently inhibited the phosphorylation of MET downstream signaling effectors, including AKT, ERK, STAT3 and PLCγ2 in a dose-dependent manner. In the cancer cell line- and patient-derived xenograft tumor models from gastric, lung and liver cancers harboring MET amplification or MET exon14 skipping mutations, TPX-0022 caused dramatic tumor regression and tumor growth inhibition, without overt abnormality and body weight loss in treated mice. Furthermore, the tumor inhibitory effect was associated with drastic inhibition of MET activity. Overall, TPX-0022 is a novel and potent MET inhibitor and has demonstrated desirable drug-like properties, a good preclinical safety profiles, that warrants further clinical development and an IND submission is currently planned. Citation Format: Dayong Zhai, Evan Rogers, Wei Deng, Xin Zhang, Dong Lee, Jane Ung, Han Zhang, Jing Liu, Yuelie Lu, John Huang, Armin Graber, Zach Zimmerman, John Lim, Jeffrey Whitten, J. Jean Cui. TPX-0022, a polypharmacology inhibitor of MET/CSF1R/SRC for treatment of cancers with abnormal HGF/MET signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1321.

In the tumor microenvironment, tumor associated macrophages (TAMs) support tumor growth by suppressing antitumor immune responses and promoting angiogenesis, which is associated with disease progression and poor clinical outcomes. In contrast to the classic phagocytic and cytotoxic pro-inflammatory M1 phenotype of macrophages engulfing and digesting pathogens, TAMs often adopt the anti-inflammatory and immune regulatory M2 phenotype in response to colony stimulating factor 1 (CSF1), which is produced by either tumor cells or stroma cells. Signaling through colony stimulating factor 1 receptor (CSF1R), a receptor tyrosine kinase expressed on the surface of mononuclear phagocytes, is involved in the recruitment of TAMs and has been associated with tumor progression and suppression of the immune response. Thus, CSF1R represents a key therapeutic target. TPX-0022, a type I kinase inhibitor with a novel macrocyclic structure, has been designed and optimized to inhibit MET/CSF1R/SRC with enzymatic kinase inhibition IC50s of 0.14, 0.76 and 0.12 nM, respectively. In a Ba/F3 ETV6-CSF1R cell model, TPX-0022 inhibited both autophosphorylation of CSF1R with an IC50 <3 nM and cell growth with an IC50 of 14 nM. In addition, TPX-0022 effectively inhibited the growth of Ba/F3 ETV6-CSF1R xenograft tumors in vivo. In the CSF1/CSF1R signaling-dependent M-NFS-60 model, TPX-0022 not only exhibited potency with an IC50 of 0.3 nM under baseline condition, but also potently inhibited the growth of M-NFS-60 cells with an IC50 of 11.6 nM in the presence of exogenous CSF1 at 1 ng/mL concentration, a condition mimicking typical in vivo conditions in the presence of advanced tumors. In contrast, in our study, the potency of the type II CSF1R inhibitor PLX-3397 demonstrated a strong dependency on the concentration of mouse CSF1, as the anti-proliferation IC50 shifted from <0.1 nM to 146.4 nM when CSF1 concentration changed from baseline to 1 ng/mL. Finally, in the MC38 syngeneic mouse model, TPX-0022 effectively reduced TAMs, altered the polarity of TAMs toward a more M1 phenotype, increased cytotoxic T cells and inhibited the growth of MC38 tumors. These preclinical results demonstrated a potent CSF1R inhibitory activity of TPX-0022 and the ability of TPX-0022 to inhibit tumor growth and promote a pro-inflammatory anti-tumor microenvironment. Citation Format: Wei Deng, Dayong Zhai, Evan Rogers, Xin Zhang, Dong Lee, Jane Ung, Han Zhang, Jing Liu, Yuelie Lu, John Huang, Armin Graber, Zach Zimmerman, John Lim, Jeffrey Whitten, J. Jean Cui. TPX-0022, a polypharmacology inhibitor of MET/CSF1R/SRC inhibits tumor growth by promoting anti-tumor immune responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1325.

ALK and ROS1 kinase inhibitors have achieved tremendous success in the treatment of lung cancer patients. However, the emergence of drug resistance limits their long term clinical applications. The mechanisms of resistance often include gene amplification, acquired mutations, bypass signaling, and epithelial-mesenchymal transition (EMT). The bypass and EMT-based resistances constitute the majority of the resistant patient population, especially after multiple kinase inhibitor treatment. None of the current ALK or ROS1 inhibitors can overcome bypass or EMT-based resistance when applied as a single agent therapy. SRC kinase has been identified to contribute broadly to cancer treatment resistance via participation in signaling pathways required for DNA synthesis, control of receptor turnover, actin cytoskeleton rearrangement, migration, adhesion, invasion, motility, and survival. SRC/FAK signaling plays important roles in regulating antitumor immunity, cancer stem-like properties, and EMT. Here we deployed a polypharmacology approach to combatting multiple resistance mechanisms spontaneously. Recombined enzyme assays, engineered cell lines and H2228 cells were used to evaluate TPX-0005 in in vitro and in vivo models. TPX-0005 is a potent ALK/ROS1/TRK inhibitor with a rigid three-dimensional macrocyclic structure and a much smaller size (MW <370) than current ALK/ROS1/TRK inhibitors. The compact structure allows TPX-0005 efficiently target the center of ATP binding site and be able to circumvent the steric interference from clinical resistant mutations. Therefore, TPX-0005 potently inhibited both wild type and mutant ALK/ROS1/TRK fusion proteins including gatekeeper and solvent front mutations at low nanomolar concentration. In addition to its primary targets, TPX-0005 is also a potent SRC/FAK inhibitor. H2228 lung cancer cell line, endogenously expressing EML4-ALKv3 protein, is refractory to crizotinib and ceritinib in cell proliferation assay (IC50 ∼1 μM). The upregulation of multiple RTKs including EGFR and IGFR, as well as cancer stem cell marker CD44 in H2228 cells is believed to confer the primary resistance to selective ALK inhibitors. Inhibition of SRC/FAK kinases will modulate RTK expression and cancer stem-like properties to restore the sensitivity to ALK inhibitor. TPX-0005 inhibited the phosphorylation of EML4-ALK (IC50 13 nM), SRC and FAK (IC50s 70-80 nM), along with other downstream signaling targets in H2228 cells, leading to dose-dependent down-regulation of EGFR and CD44 expression levels. As a result, TPX-0005 overcame the primary resistance and effectively inhibited cell proliferation (IC50 ∼0.1 μM) and cell migration of H2228 cells. TPX-0005 exerts unprecedented polypharmacology profile for combatting multiple resistance mechanisms including acquired mutations, bypass signaling, cancer stemness, and metastasis, that warrants further clinical investigation.